The reason that SDN startups are getting gobbled up is because
SDN is a new technology that turns enterprise networking on its
ear. Instead of buying expensive routers and switches with a lot
of fancy features from the likes of Cisco, companies can buy simpler, cheaper
hardware—and less of it. This makes networks more flexible and
less expensive than they are today.

The market is projected to grow from $360 million in 2013 to $3.7
billion by 2016.